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| United States Patent |
6,204,767
|
|
Sparks
|
March 20, 2001
|
Chair monitor
Abstract
A chair monitoring system is used in a nursing home, hospital, healthcare
facility or home or in a vehicle application, to detect an individual's
attempted departure from a seat before the individual leaves the seat, or
as an individual starts to slide out of a seated position. The purpose of
this invention is to help prevent falls and provide an early alarm to
enable caregivers, nursing staff, or another responsible individual to
respond quickly and appropriately to reduce injuries. This alarm can be
audible and visual at the chair and/or can trigger a nurse call system. A
new technology is used to continually, invisibly, and remotely monitor a
person's presence in a chair. There are no pads, strings, clips or
attachments to the monitored person. The safe area can be easily adjusted
to fit the specific needs of the situation and enable a caregiver to be
alerted when a person slides down, leans forward or starts to leave the
chair before he or she has physically left the chair. Any size or weight
person can be monitored. Electronic technology is used to accurately
detect the distance without physically touching the monitored person.
| Inventors:
|
Sparks; Brian J. (Milwaukee, WI)
|
| Assignee:
|
Edwards; Donald A. (Mequon, WI)
|
| Appl. No.:
|
326430 |
| Filed:
|
June 4, 1999 |
| Current U.S. Class: |
340/573.1; 340/573.7; 340/686.1; 340/686.6; 367/93; 367/99 |
| Intern'l Class: |
G08B 023/00 |
| Field of Search: |
340/573.1,686.6,686.1,573.7,575,667,552,555,435,903
180/735
250/222.1
128/781
367/99,93
|
References Cited
U.S. Patent Documents
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|
| 3991746 | Nov., 1976 | Hanna | 128/2.
|
| 4175263 | Nov., 1979 | Triplett et al. | 340/573.
|
| 4179692 | Dec., 1979 | Vance | 340/573.
|
| 4196425 | Apr., 1980 | Williams, Jr. et al. | 340/573.
|
| 4197528 | Apr., 1980 | Gibson | 367/93.
|
| 4203098 | May., 1980 | Muncheryan | 340/575.
|
| 4242672 | Dec., 1980 | Gault | 340/573.
|
| 4295133 | Oct., 1981 | Vance | 340/573.
|
| 4484043 | Nov., 1984 | Musick et al. | 200/85.
|
| 4565910 | Jan., 1986 | Musick et al. | 200/85.
|
| 4583084 | Apr., 1986 | Henderson et al. | 340/573.
|
| 4633237 | Dec., 1986 | Tucknott et al. | 340/573.
|
| 4750584 | Jun., 1988 | Tanaka et al. | 181/68.
|
| 4858622 | Aug., 1989 | Osterweil | 128/782.
|
| 4890266 | Dec., 1989 | Woodward | 367/99.
|
| 4907845 | Mar., 1990 | Wood | 340/573.
|
| 4947152 | Aug., 1990 | Hodges | 340/573.
|
| 4949074 | Aug., 1990 | D'Ambrosia et al. | 340/552.
|
| 4980869 | Dec., 1990 | Forster et al. | 367/99.
|
| 5057819 | Oct., 1991 | Valenti | 340/573.
|
| 5066943 | Nov., 1991 | Demirel et al. | 340/573.
|
| 5144284 | Sep., 1992 | Hammett | 340/573.
|
| 5184112 | Feb., 1993 | Gusakov | 340/573.
|
| 5235319 | Aug., 1993 | Hill et al. | 340/573.
|
| 5410297 | Apr., 1995 | Joseph et al. | 340/573.
|
| 5469861 | Nov., 1995 | Piscopo et al. | 128/781.
|
| 5471198 | Nov., 1995 | Newham | 340/573.
|
| 5494046 | Feb., 1996 | Cross | 128/782.
|
| 5500526 | Mar., 1996 | Shalvi et al. | 250/222.
|
| 5519380 | May., 1996 | Edwards | 340/572.
|
| 5572484 | Nov., 1996 | Gaus et al. | 367/99.
|
| 5600305 | Feb., 1997 | Stafford et al. | 340/573.
|
| 5602542 | Feb., 1997 | Widmann | 340/903.
|
| 5603127 | Feb., 1997 | Veal | 4/246.
|
| 5635905 | Jun., 1997 | Blackburn et al. | 340/555.
|
| 5654694 | Aug., 1997 | Newham | 340/573.
|
| 5872507 | Feb., 1999 | Weber et al. | 340/435.
|
| 5914660 | Jun., 1999 | Mesibov et al. | 340/573.
|
| 5943295 | Aug., 1999 | Varga et al. | 367/99.
|
| 5990799 | Nov., 1999 | Boon et al. | 340/667.
|
Other References
Advertisement for Posey Personal Alarm, p. 14.
Advertisement for Tabs Mobility Monitor, Provider Magazine, Sep., 1998, p.
96.
Article for Tabs Mobility Monitor, pp. 1-2.
Posey Healthcare Products Guide, Prevent Falls Without Resorting to
Restraints. 2 pages.
Advertisement for Bed-Check Corporation, p. 6, Contemporary Long Term Care
Magazine.
Bed-Check Control Unit information sheet.
|
Primary Examiner: Lee; Benjamin C.
Assistant Examiner: Nguyen; Phung
Attorney, Agent or Firm: Boyle Fredrickson Newholm Stein & Gratz SC
Claims
What is claimed is:
1. A contactless monitoring system comprising:
(A) a controller which is configured to monitor an individual seated in a
seat, said controller including
(1) a transmitter which is configured to transmit a pulsed signal at
intervals;
(2) a receiver which is configured to receive the reflected signals from
the monitored individual; and,
(3) a circuit which is coupled with the transmitter and the receiver and
which is configured to
a) measure the actual return time of each pulsed signal from the time of
signal transmission toward the individual to the time of the receipt of
the reflected signal from the individual, and
b) compare the return time to a threshold return time parameter, wherein
the threshold return time parameter corresponds directly to at least one
boundary of a three-dimensional space parameter that corresponds to a
location beyond which the monitored individual would move when in danger
of leaving the seat; and
(B) an alarm generator which is coupled with the circuit and which
generates an alarm signal when the circuit determines that the return time
of at least one pulsed signal exceeds the threshold return time parameter,
thereby indicating that the monitored individual is in danger of leaving
the seat.
2. A system as defined in claim 1, wherein the pulsed signal is an infrared
light.
3. A system as defined in claim 1, wherein the pulsed signal is a sonic
signal.
4. A system as defined in claim 1, wherein the controller is mounted on a
low back chair.
5. A system as defined in claim 4, wherein the controller is mounted on
said low back chair with a mounting apparatus comprising an extension
strip mounted between said controller and the back of said low back chair.
6. A system as defined in claim 4, wherein the low back chair is one of a
stationary chair and a wheelchair.
7. A system as defined in claim 1, wherein the controller is mounted on a
high back seating apparatus.
8. A system as defined in claim 7, wherein said controller is received into
a compartment formed within a headrest or lumbar support and is mounted on
the back of said high back seating apparatus.
9. A system as defined in claim 7, wherein the high back seating apparatus
is a vehicle seat.
10. A system as defined in claim 1, wherein the three-dimensional space
parameter has an outer boundary which is variable, by varying the
threshold return time parameter, within the range from approximately 6
inches to approximately 30 inches.
11. A system as defined in claim 1, wherein the threshold return time
parameter corresponds directly to the sensitivity of the positional change
of the monitor at an outer boundary of the three-dimensional predetermined
space parameter.
12. The system as defined in claim 11, wherein the sensitivity of
positional change is 1 cm.
13. A system as defined in claim 1, wherein the pulsed signals are
transmitted at a rate of approximately one per second.
14. A system as defined by claim 1, wherein the pulsed signals are
transmitted at a frequency of 20 kHz to 100 kHz.
15. A system as defined in claim 1, wherein the transducer is Polaroid's
electrostatic transducer of environmental grade, 600 series, part #616342
& 607281 used in conjunction with a 6500 Series Transformer, part #619392
& 619391.
16. A system as defined in claim 1, wherein said alarm generator is reset
by pushing a button mounted on said controller.
17. A system as defined in claim 1, wherein the transmitter and receiver
are combined in a single transducer.
18. A contactless monitoring system comprising:
(A) a controller for monitoring an individual located within a specified
spacing from the controller, said controller comprising
(1) a single transducer which transmits reflectable pulsed sonic signals
toward a monitored individual at intervals and which receives reflected
signals from the monitored individual;
(2) a counter which is coupled with the transducer and which measures the
actual return time of each pulsed signal and compares the return time of
each pulsed signal with a preset return time range, wherein the preset
return time range corresponds directly to at least two boundaries of a
three dimensional predetermined space parameter, wherein at least one of
the boundaries corresponds to a location beyond which the monitored
individual would move when in danger of leaving the seat; and
an alarm generator which is coupled with the counter and which generates an
alarm signal when the counter measures a reflected pulsed signal having a
return time which is outside the preset return time range, the alarm
generator generating the alarm whenever the monitored individual moves
outside of any of the monitored boundaries of the three dimensional space.
19. A method of monitoring a seated individual, comprising:
mounting a monitoring system at a distance from the individual to be
monitored;
transmitting, from the monitoring system, a series of pulsed signals,
wherein the transmitted signals are transmitted toward the monitored
individual seated on a seating apparatus so that the pulsed signals are
reflected off the monitored individual and back toward said monitoring
system;
receiving the pulsed signals at the monitoring system;
comparing the return time of each pulsed signal to a threshold return time
range which corresponds directly to at least one boundary of a
three-dimensional predetermined space parameter that corresponds to a
location beyond which the monitored individual would move when in danger
of leaving the seat;
generating an alarm signal only if the return time of a pulsed signal is
outside the threshold return time range, thereby indicating that the
monitored individual is not within the three-dimensional space parameter,
wherein an alarm signal is generated whenever the monitored individual is
in danger of leaving the seat.
20. A method as defined in claim 19, further comprising deactivating the
alarm and automatically resetting the alarm generator if the monitored
individual returns to within said three-dimensional predetermined space
parameter when subsequent pulses are detected.
21. A method as defined in claim 19, wherein the pulses are transmitted at
intervals of not more than one second.
22. A method as defined in claim 19, wherein the pulsed signals are
transmitted at a periodic pulsed rate of approximately one per second.
23. A contactless monitoring system comprising:
(A) a controller which is configured to monitor an individual seated in a
seat, said controller including
(1) a transmitter which is configured to transmit a pulsed signal at
intervals;
(2) a receiver which is configured to receive reflected signals from the
monitored individual; and,
(3) a circuit which is coupled with the transmitter and with the receiver
and which is configured to
a) measure an intensity-independent characteristic of each pulsed signal
that is transmitted from the transmitter, reflected from the monitored
individual, and impinged upon the receiver, and
b) compare the measured characteristic to a range of characteristics having
a maximum threshold parameter of the measured characteristic and a minimum
threshold parameter of the characteristic, wherein the threshold
parameters correspond directly to at least two boundaries of a
three-dimensional space parameter, wherein at least one of the boundaries
corresponds to a location beyond which the monitored individual would move
when in danger of leaving the seat; and
(B) an alarm generator which is coupled with the circuit and which
generates an alarm signal when the circuit determines that the measured
characteristic of at least one pulsed signal is either less than the
minimum threshold parameter or greater than the maximum threshold
parameter, and wherein an alarm signal is generated whenever the monitored
individual is in danger of leaving the seat.
24. A system as defined in claim 23, wherein the measured characteristic of
each signal is a phase shift between the transmitted signal and the
received signal, and wherein the threshold parameter range is a phase
having a maximum threshold phase shift and minimum threshold phase shift,
said alarm generator generating said alarm signal whenever the measured
phase shift is determined as being either less than the minimum threshold
phase shift or greater than the maximum threshold phase shift.
25. A system as defined in claim 23, wherein the measured characteristic of
each signal is the angle of incidence of the reflected signal, and wherein
the threshold parameter range is a range of threshold angles of incidence
having a maximum threshold angle of incidence and minimum threshold angle
of incidence, said alarm generator generating said alarm signal whenever
the measured phase shift is determined as being either less than the
minimum threshold angle of incidence or greater than the maximum threshold
angle of incidence.
26. A system as defined in claim 25, wherein the circuit includes a Sharp
GP2D02 position sensitive detector.
27. A system as defined in claim 23, wherein the measured characteristic of
each signal is the return time between transmission of the reflected
signal and receipt of the signal, and wherein the threshold parameter
return time range having a maximum threshold return time and minimum
return time, said alarm generator generating said alarm signal whenever
the measured return time is determined as being either less than the
minimum threshold return time or greater than the maximum threshold return
time.
28. A system as defined in claim 23, wherein the transmitter and the
receiver are combined in a single transducer.
29. A monitoring system as recited in claim 1, wherein the threshold time
parameter is a time range having a minimum threshold return time and the
maximum threshold return time, and wherein the alarm generator generates
the alarm signal whenever the measured return time is determined as being
either less than the minimum threshold return time or greater than the
maximum threshold return time.
30. A method as defined in claim 19, wherein the alarm signal is generated
immediately after determining that the return time of any one pulsed
signal is outside of the predetermined range.
31. A method as defined in claim 19, wherein the transmitting and receiving
steps are performed by a single transmitter and a single receiver located
behind a forward-facing seated individual.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a contactless monitoring system and, more
particularly, to a monitoring system for monitoring an individual seated
in a chair.
2. Discussion of the Related Art
As the population ages, an increasing number of people are developing
dementia, or disorientation and are in nursing homes or home caregiving
situations where falls from a stationary chair, wheelchair, couch, etc.
can result in severe injuries. This type of situation is not only
dangerous for the demented individual, but can also be very stressful to
the caregiver or nursing staff. Since the nursing staff in most facilities
or home caregivers cannot continually watch a person who may fall from a
chair, they must rely on the assistance of monitors to alert them if a
person attempts to leave the chair or has fallen out of it.
Patients in nursing homes and hospitals are often very frail and
predisposed to falling. Unfortunately for these patients, the slightest
fall may result in a severe, potentially permanent injury that may lead to
the deterioration of a person's physical well being and ultimately to his
or her death. Many of these falls occur because an individual attempts to
stand or walk without assistance. In addition, people may fall asleep in a
seated position and gradually slide down, slump or fall forward and then
fall out of the seat. This situation is of utmost concern to nursing
staffs in hospitals and nursing homes and to home caregivers because it is
often difficult to detect the patient's change in condition unless a staff
member or caregiver is sitting right next to the individual.
Unfortunately, in this time of cost containment and cutbacks of medical
personnel, it is often impossible to have a staff member assigned to only
one patient. In addition, it is unrealistic to expect a home caregiver to
be with a loved one twenty-four hours a day. Accordingly, a simple,
inexpensive method of monitoring the movements of a seated patient without
requiring a caregiver to constantly observe the patient or loved one is
needed.
In addition, the use of the current monitoring systems is often limited to
a home or medical facility. Because of the size and complexity of many
monitoring systems, they cannot be easily transported or used in a
contained area such as a car or other vehicle. Furthermore, the current
monitoring systems cannot detect changes in the head and body position
such as slumping, slipping or falling backwards, which are indicative of
sleepiness and extremely significant for an individual seated in a chair
and for the operator of a vehicle.
Numerous methods for preventing falls from chairs or at least for detecting
such falls currently exist. For instance, physical restraints are commonly
used to prevent the monitored person from exiting a chair, wheelchair or
other seating apparatus. Although the use of physical restraints is
effective in confining the individual to a specific area, the use of
physical restraints results in physical and psychological side effects.
These effects include psychological stress resulting from the individual's
perceived loss of his or her of freedom and dignity, and physical injury
resulting from struggling to be free of the restraints. Physical
restraints obviously are of no use in vehicular applications.
Electronic monitoring devices help alleviate many of the physical and
psychological side effects resulting from the use of physical restraints
and have a wider range of uses. These monitoring systems generally fall
into three major categories.
The first category of monitoring system is a weight or pressure detecting
system that uses a pressure sensitive pad and controller to detect the
weight of a person. To be detected, a person must sit on top of the pad
and must be of adequate weight to compress contacts of the pad. Operation
of the system depends upon the pad springing back into place when the
person leaves the seat. The resulting mechanical action is detected with a
mechanical or electronic piezoelectric switch, which sends a signal to a
controller that triggers an alarm. There are many drawbacks to this type
of system. The alarm is only activated if the monitored individual leaves
the chair completely. It also does not provide any mechanism for detecting
mere changes in the individual's position indicating an immanent
departure. In addition, many of these systems have a time delay before the
alarm is sounded to reduce nuisance alarms. Unfortunately, the time delay
prevents the alarm from sounding until after the monitored person has
already fallen. In addition, the monitoring pads must be replaced
frequently because they are easily damaged and rendered inoperable.
Pressure activated monitors are often ineffective for small and frail
people or children because those people may not be heavy enough to
compress the pressure pad sufficiently to activate the alarm.
The second category of monitoring devices or systems utilizes a physical
attachment connected between a monitored individual and a controlling
device. This system typically requires a clip and string or cord to be
attached to the patient's clothes. The other end of the string is
connected to a magnet or insert that plugs into the controlling device.
When a person attempts to leave the chair, the insert is pulled out of the
controlling device to trigger an alarm. There are many disadvantages to
this monitoring system. The clip may be removed by the monitored
individual, or it can simply fall off the monitored individual. If the
clip is removed, the device is rendered ineffective. The string also needs
to be of the proper length. If it is too long, it can wrap around the
monitored individual and cut off circulation. The attached clip may cause
a degree of discomfort that causes the monitored individual to try to
remove it. Consequently, nursing staff and caregivers must continually
check to make sure the clip is attached to the patient. If the insert is
pulled out of the controller, the controller triggers an alarm. Once the
alarm is activated, a staff member or caregiver must reset the device and
reattach the insert and/or clip even if the monitored individual returns
immediately to a seated position.
The third category of monitoring devices or systems use intensity-based
measurements of transmitted energy beams to detect if the monitored person
is moving into an unsafe area. Under this type of system, a transmitter is
positioned in one location near the patient. A receiver is positioned in a
second location so that it continually receives the transmitted beam when
the patient is in a desired position. If the individual moves outside the
desired position, the beam is broken and an alarm is triggered. Although
this approach does not require any of the restrictive methods as required
in the two previous categories and has a wider range of applications, it
only indicates the presence or absence of the monitored individual in the
transmitted area. It cannot detect small changes in the patient's
position, such as slumping.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a chair monitoring
system which may be used by non-ambulatory persons of all sizes and
weights and which does not require the person being monitored to actually
leave the chair before generating an alarm. "Non-ambulatory," as used
herein, is not limited to persons incapable of walking. Rather, a
non-ambulatory" person is one who is in a chair or other confined space
and who is not expected to walk or otherwise move from that space during
the monitoring period.
It is another object of this invention is to provide a mechanism to reduce
falls from a sitting position by generating an alarm before a person
leaves the defined area or when the person starts to lean forward, slide
down, or slump.
It is another object of this invention is to provide a fast and immediate
alarm to enable caregivers to respond to an attempted egress before an
injury occurs or the person has fallen.
It is another object of this invention to reduce the use of restraints and
attachments.
It is another object of this invention is to provide an automatic reset
when a monitored person returns to the safe area. The reset will occur if
the patient immediately returns to the safe area, thus eliminating the
need for the staff to respond to an attempted egress or slumping situation
when the person has returned to the safe area. This eliminates nuisance
alarms while enabling staff to respond to real departures.
It is another object of this invention is to provide an automatic reset
that does not depend upon a mechanical action, weight or attachments to
the person.
It is another object of this invention is to use new electronic technology
to continually monitor a person's position and provide immediate feedback
and alarm if a person starts to leave the safe area.
It is another object of the present invention to eliminate the effects of
individual patient differences, such as differences in clothing color and
type, on the effectiveness of the monitoring system.
It is another object of this invention is to improve safety, reduce
nuisance alarms and allow the caregiver and nurses to adjust the distance
of the safe area to accommodate the specific needs of the individual being
monitored.
It is another object of this invention is to provide caregivers with an
immediate warning without time delays between a change in the monitored
individual's position and the alarm signal.
It is another object of this invention is to provide a monitor capable of
monitoring low weight, frail people and children.
It is another object of this invention is to provide a monitoring system
that does not require the use of physical restraints, clips, strings,
wires or other devices that attach to the monitored person.
It is another object of this invention is to eliminate costly replacement
pads and other mechanical means of monitoring a person in a chair.
It is another object of this invention is to provide a device that be
readily used and mounted on a wheelchair, chair, vehicle headrest,
commode, walker or couch.
These objects are achieved by providing a self-contained, contactless,
chair mounted monitoring system that relies on a direct correlation
between 1) the distance between a controller of the system and a monitored
individual, and 2) an intensity-independent characteristic of the
reflected signal. The distance could be measured, e.g., using pulse
timing, phase comparison, or optical parallax, either static or dynamic.
For example, as the distance between the controller and individual
increases, so does the return time of the reflected pulsed signal.
Likewise, as the distance between the controller and the individual
decreases, so does the return time of the reflected pulsed signal. Similar
distance based correlations exist with respect to phase shift and angle of
incidence and possibly other intensity-independent characteristics of the
signal. An alarm signal is generated whenever the measured characteristic
of the returned signal does not meet a threshold requirement. In
time-based applications, the threshold will typically be set near the
maximum return time in applications in which only chair egress is of a
concern, but may also be a smaller return time in other applications in
which slumping backwards or sideways is of a concern.
The system functions by placing the device having a transmitter and
receiver, which may be combined in a single transducer, at a
predetermined, settable distance from a monitored individual and
transmitting a pulsed signal toward the individual at intervals. The
transmitted beam is then reflected off the monitored individual and back
to a receiver on the controller. The system then measures the return time,
phase shift, or angle of incidence of the received signal and compares it
to a preset range for the measured selected characteristic. The preset
range corresponds directly to a three-dimensional predetermined space
parameter selected by, e.g., a caregiver. The three-dimensional
predetermined space parameter is essentially the space or area that is
considered safe, or normally occupied by a person in a seated position. If
the monitored individual goes outside of the three-dimensional
predetermined space parameter, he or she is presumed to no longer be in a
safe or normal position and should therefore be checked by the staff or
caregiver.
The receiver is coupled to a circuit that measures an intensity-independent
characteristic of each returned pulsed signal, such as the return time of
the reflected transmitted signals, and compares it with the corresponding
predetermined space parameter for the monitored individual. If the
measured characteristic is outside the preset threshold parameter, the
circuit triggers an alarm. In a caregiver application, the alarm signal
alerts the medical staff or home caregiver that the patient is no longer
within the predetermined space monitored by the system. In a vehicular
application, the signal warns the driver that he or she is inattentive or
falling asleep.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred exemplary embodiments of the invention are illustrated in the
accompanying drawings in which like reference numbers are presented
throughout, and in which:
FIG. 1 schematically illustrates a contactless chair monitoring system
constructed in accordance with a first embodiment of the invention;
FIG. 2 is a perspective view of the monitor of the system, shown from the
front of the monitor;
FIG. 3 corresponds to FIG. 2 and illustrates the rear of the monitor;
FIG. 4 is a top plan view of the monitor;
FIG. 5 is a bottom plan of the monitor;
FIG. 6 schematically illustrates the electronic components of the
controller;
FIG. 7 is a flow chart outlining a method of monitoring a patient with the
contactless monitoring system of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
1. Resume
The present invention provides a self-contained contactless monitoring
system for detecting undesired movement of a person seated in a chair. The
monitoring system provides a safe and effective method of monitoring a
seated individual without the use of any physical restraints or
attachments. The monitoring system utilizes a monitoring method based upon
a direct correlation between 1) a change in an intensity-independent
characteristic of a pulsed signal generated by the controller and
reflected from the individual and, 2) a change in the distance between the
controller and the monitored individual. As the distance between the
controller and individual increases, so does the measured characteristic
of the reflected pulsed signal. Likewise, as the distance between the
controller and the individual decreases, so does the measured
characteristic. The measured characteristic may, for instance, be a phase
shift between the transmitted and received signals, the angles of
incidence of the received signal, or preferably, the return time of the
received signals.
The Chair Monitor Device
Referring now to FIG. 1, a contactless patient monitoring system 10
constructed in accordance with the invention can easily be mounted onto
the back 12 of a chair 14, such as a wheelchair, vehicle headrest or
stationary chair, at a predetermined distance from an individual 16 to be
monitored. The monitoring system is preferably mounted on the backrest 12
of a chair 14 behind the monitored individual 16 as depicted in FIG. 1, to
reduce the possibility that the individual 16 will tamper with the
monitoring system 10. The mounting location and mounting technique will
vary from application to application. For instance, the patient monitoring
system 10 can be mounted onto the backrest 12 of a high back seating
apparatus, such as a vehicle seat, with a specially adapted cushioned
headrest or lumbar support. The cushioned headrest (not shown) of such a
seat has a compartment designed to receive the patient monitoring system
10. The compartment has a pouch or otherwise opens to the back of the
headrest so that the patient monitoring system can easily be mounted
within it. An aperture extends from the inner wall of the compartment
through the front surface of the cushioned headrest. When the patient
monitoring system 10 is housed within the compartment, the aperture aligns
with a transducer of the monitoring system, allowing the transducer to
transmit pulsed signals toward the monitored individual without
interference. The headrest may also be mounted onto the backrest of a high
back seating apparatus by slipping an adjustable strap secured to both
sides of the headrest over the backrest and then tightening the straps
into place.
Alternatively, the patient monitoring system can be mounted onto the
backrest 12 of a low back seating apparatus such as a wheelchair or other
chair 14. In this circumstance, an extension strip (not pictured) made of
sturdy, resilient material, such as plastic or Plexiglas, can be secured
onto the backrest 12 of the chair 14. The strip is formed into lower,
middle and top sections that create a shelf for the cushioned headrest.
The lower section, preferably about twelve inches long, is mounted
directly onto the backrest 12 of the chair 14 and extends vertically
toward the back of the monitored individual's head. The lower section is
mounted onto the backrest 12 with VELCRO.RTM. or with mushroom head
fastener strips attached to the front face of the lower section or with
any other suitable connector. The middle section, preferably about three
inches long, extends from the lower section at an angle of approximately
120.degree.-135.degree. so that the middle section creates a shelf
designed to hold the patient monitoring system 10 when the extension strip
is mounted onto the backrest 12 of the chair 14. In addition, the middle
section has an aperture for accommodating wires connected to the patient
monitoring system 10 if the system 10 is powered by an external source or
connected to a nurse call system. The top section, also preferably about
31/2 inches long, extends from the middle section at approximately a right
angle essentially forming a back to the shelf created by the middle
section. The patient monitoring system 10 is mounted on the shelf created
by the middle section and top section of the extension strip, and secured
on the back surface of the patient monitoring system 10 and the inner
surface of the top section of the extension strip.
Referring now to FIGS. 2-6, the monitoring system 10 includes a controller
54 coupled to an alarm generator (not pictured) enclosed within a housing
15. The monitoring system 10 is lightweight and self-contained so that a
monitored individual 16 is not in danger of becoming entangled in cords,
connecting wires or the like. The monitoring system 10 may be powered by a
battery enclosed within a compartment 28 of the housing 15 and/or via an
external power source connecting to the housing 15 at a port 26. If the
power to the patient monitoring system 10 is low, the alarm generator will
generate a low battery tone to alert the caregiver or staff that the power
is low.
The patient monitoring system 10 is turned on and off by a pair of buttons
18, preferably mounted on the top edge of the housing 15. Advantageously,
the system can be activated by pushing only one of the buttons 18, but
both buttons 18 must be pushed simultaneously to deactivate the system.
This provides an additional safeguard to ensure the monitoring system 10
is not accidentally deactivated by the patient or staff member. In
addition, the alarm generator will generate an alarm signal when the two
buttons 18 are depressed so that any attempt to deactivate the system can
be monitored. The alarm is automatically reset when the patient returns to
the safe position or the system is turned off by depressing both buttons
18.
The controller 54 further includes a transducer 20, which is capable of
transmitting and receiving pulsed signals periodically at a rate of
approximately one signal per second at a frequency of 20-100 kHz. The
pulsed signal may be infrared, sonic, ultrasonic, microwave or any other
reflectable energy source, preferably sonar. The transducer preferably
used in the patient monitoring system 10 is Polaroid's electrostatic
transducer of environmental grade, 600 series, part #616342 & 607281 used
in conjunction with a 6500 Series Transformer, part #619392 & 619391. The
circuit is coupled with the receiver of the transducer 20 so as to measure
an intensity-independent characteristic of the reflected signal and to
compare it with preset threshold parameters.
For example, in the case of time-based measurements, the preset return time
range is defined by and corresponds directly to the predetermined space
parameter, indicating the maximum safe distance of the monitored
individual from the transducer depending on the application. The distance
may typically vary from within the range of approximately 0 inches to
approximately 30 inches, but larger distances can be provided for special
applications. The space parameters may be adjusted to new parameters with
a long-short control 22 usable to set the circuit to recognize a return
time range.
An alarm generator is coupled with the circuit to generate an alarm if the
return time or other measurement characteristic measured by the circuit is
outside the preset range. The alarm may be an audible or visible alarm
provided on the controller, or may be a signal transmittable to a remote
nurses call station. Parameters of the alarm, such as volume, duration, or
pulse period, can be adjusted with the alarm setting switch 24 located on
the side edge of the housing 15.
3. The Method of Monitoring an Individual with the Chair Monitor
Referring now to FIGS. 1, 6 and 7, the contactless patient monitoring
system 10 provides an easy and inexpensive method of monitoring an
individual seated in a chair. The patient monitoring system 10 is mounted
on the back 12 of a stationary low back chair 14, stationary high back
chair, vehicle headrest, or wheelchair, commode, etc. at a predetermined
distance from the individual 16 to be monitored. The system and alarm are
then activated in step 32 and the controller alarm setting is set to a
desired distance range in step 34. Once set to a desired distance range,
the alarm setting does not have to be reset unless the desire safe area is
redefined. The transmitter is then automatically activated in step 36 to
transmit a pulsed signal at a predetermined periodic time interval in step
38, preferably once every one-half second to once every second, toward a
monitored individual and reflected back toward the receiver. The
transmitted signal is not confined to any angle, signal frequency or
signal strength. Because the patient monitoring system 10 measures only a
specific, intensity-independent characteristic of the reflected signal,
devices used to shield the monitoring system from other energy sources,
which would be required in an intensity-based electronic monitoring
systems, are not needed with the patient monitoring system 10. The
individual 16 is continuously monitored, even if he or she is no longer
within a predetermined space parameter defined by the system. Counters of
the circuit are set in step 40 to enable it to detect whether the
monitored individual is within the predetermined space parameter that
defines and corresponds directly to defined threshold parameters such as,
a preset maximum and/or minimum return time. The circuit then compares an
actual characteristic of the reflected signal, such as the return time of
the pulsed signals, with a preset threshold of the characteristic, such as
preset a return time threshold parameter, in step 42.
If the actual parameter measured by the circuit is greater than a maximum
threshold parameter and/or less than a minimum threshold parameter, the
circuit activates an alarm generator in step 44 to trigger an alarm
signal. The alarm signal generated may be a voice warning, an optical
warning or, preferably a sound generated at a frequency within the range
including from 480 Hz to 25 kHz, and preferably about 4 kHz. The procedure
then goes to step 50 and the circuit is put to sleep. If the answer to the
inquiry of step 42 is NO, indicating that the monitored individual has not
left the safe area, the alarm generator is deactivated in step 48 and the
alarm circuit is put to sleep in step 50 until the next pulse is generated
via execution of the return step 52.
Although the time-based measurement is preferred, the system may
alternatively measure a phase shift between the transmitted and received
signals or a change in the angles of incidence of the transmitted and
received signals.
Hence, if the measured characteristic is the phase shift between the
transmitted and received signals, the phase shift of each transmitted and
received signal is measured and compared to a preset phase shift threshold
parameter. If a measured phase shift is outside of the preset phase shift
threshold parameter, the alarm generator is activated. If the phase shift
between the next transmitted and received signal is also outside the
preset phase shift threshold, the alarm generator will continue to
generate an alarm signal. If the phase shift between the next transmitted
and received signal is within the defined phase shift threshold parameter,
the alarm generator is reset.
Similarly, if the measured characteristic is the angle of incidence of the
reflected signal, the angle of incidence of each transmitted and received
signal is measured by the circuit, preferably using a position sensitive
detector such as the Sharp GP2D02 position sensitive detector, and
compared to the preset angle of incidence threshold parameter. If a
measured angle of incidence is outside of the preset angle of incidence
threshold parameter, the alarm generator is activated. If the angle of
incidence of the next transmitted and received signal is also outside of
the preset angle of incidence threshold parameter, the alarm generator
continues to generate an alarm signal. If the next measured angle of
incidence is within the preset angle of incidence threshold parameter, the
alarm generator is reset.
The patient monitoring system 10 continues to monitor the individual 16,
even if he or she is no longer within the predetermined space parameter.
Therefore, unlike other electronic monitoring systems which only indicate
the presence or absence of an individual at a specific point, an alarm
signal generated by the patient monitoring system indicates that, although
the monitored individual may still be present within the monitored area,
he or she has gone outside the preset space parameter into an unsafe area.
This feature provides much more specific and refined monitoring and also
allows minimum and maximum predetermined distance parameters to be
monitored simultaneously. It is also very precise, being capable of
detecting location of the monitored individual 16 within 1 cm. The breadth
of monitoring range, combined with the ability to measure a change in
position as small as 1 cm, allows the patient monitoring system 10 to
monitor an individual in a vehicle seat as effectively as an individual in
a wheelchair.
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